Search

NiTi Shape Memory Alloy (SMA) finds wide applications in high-performance engineering industries such as medical devices, micro-electrical and electronic components, aerospace, aircraft structure, and so on, to name a few. This is owing to its superior properties like shape memory effect (SME), superelasticity, and biocompatibility. However, getting a proper joining of NiTi alloys is hard considering its unique characteristics. Therefore, joining this alloy has been a domain of great attention for scientists. The current research work investigates the weldability of NiTi wires using Laser spot welding. The microhardness and the tensile strength of the weld joint are acquired according to Taguchi's design of experiment. The significance of the control factors (laser power, scan speed, and focal length) is identified through ANOVA, and an ideal factor setting for optimum individual responses is established. Moreover, simultaneous optimisation of multi-performance characteristics is also attempted through Grey Relational Analysis (GRA) method. From the GRA, 300 W laser power, 1 mm/sec scan speed, and 0.5 mm focal position are found to be giving optimum results for both the responses. The result from the confirmation runs showed that the predicted optimal welding parameters improve the individual as well as the multiple performance characteristics. [ABSTRACT FROM AUTHOR]

Nonlinear frequency responses of the laminated carbon/epoxy composite curved shell panels have been investigated numerically and validated with in-house experimentation. The nonlinear responses have been computed numerically via customised computer code developed in MATLAB environment with the help of current mathematical model in conjunction with the direct iterative method. The mathematical model of the layered composite structure derived using various shear deformable kinematic models (two higher-order theories) in association with Green- Lagrange nonlinear strains. The current model includes all the nonlinear higher-order strain terms in the formulation to achieve generality. Further, the modal test has been conducted experimentally to evaluate the desired frequency values and are extracted via the transformed signals using fast Fourier transform technique. In addition, the results are computed using the simulation model developed in commercial finite element package (ANSYS) via batch input technique. Finally, numerical examples are solved for different geometrical configurations and discussed the effects of other design parameters (thickness ratio, curvature ratio and constraint condition) on the fundamental linear and nonlinear frequency responses in details. [ABSTRACT FROM AUTHOR]

In this paper we present a mathematical analysis for the magneto hydrodynamic (MHD) axi-symmetric stagnation-point flow and heat transfer over a shrinking sheet which shrinks axi-symmetrically in its own plane. The governing partial differential equations along with the boundary conditions are first cast into a dimensionless form and then these equations are solved numerically by shooting technique. Thermal conductivity is assumed to vary linearly with the temperature. Temperature profiles are obtained for two different types of heating process namely (i) the sheet with prescribed surface temperature (PST) and (ii) the sheet with prescribed surface heat flux (PHF). The effects of various physical parameters on the flow and heat transfer characteristics are presented graphically and discussed. [ABSTRACT FROM AUTHOR]

This work is concerned with the numerical study of laminar, steady MHD mixed convection flow, and entropy generation analysis of A l 2 O 3 -water nanofluid flowing in a lid-driven trapezoidal enclosure. The aspect ratio of the cavity is taken very small. The cavity is differentially heated to study the fluid flow, heat, and mass transfer rate. The adiabatic upper wall of the enclosure is allowed to move with a constant velocity along the positive x -direction. The second-order finite difference approximation is employed to discretize the governing partial differential equations, and a stream-function velocity formulation is used to solve the coupled non-linear partial differential equations numerically. The simulated results are plotted graphically through streamlines, isotherms, entropy generation, Nusselt number, and Sherwood number. The computations indicate that the average Nusselt number and average Sherwood number are decreasing functions of Hartmann number, aspect ratio, and nanoparticle volume fraction. Significant changes in streamlines, temperature and concentration contours for high Richardson number are observed., Competing Interests: The authors declare no conflict of interest., (© 2021 Published by Elsevier Ltd.)

A numerical investigation of entropy generation, heat and mass transfer is performed on steady double diffusive natural convection of water-based Al 2 O 3 nanofluid within a wavy-walled cavity with a center heater under the influence of an uniform vertical magnetic field. The top horizontal wavy wall, left and right vertical walls of the enclosure are kept at low temperature and concentration of T c and c c whereas central part of the bottom horizontal wall is maintained at high temperature and concentration of T h and c h and the remaining part is kept adiabatic where temperature and concentration gradient are taken as zero. The Bi-CGStab method and Tri-diagonal algorithm are used to solve the governing equations. The study has been performed for several relevant parameters such as Rayleigh number ( 10 3 ≤ R a ≤ 10 5 ), Hartmann number ( 0 ≤ H a ≤ 60 ), buoyancy ratio number ( - 2 ≤ N ≤ 2 ), volume fraction of nanoparticles ( 0.0 ≤ ϕ ≤ 0.2 ) and different undulation number of the upper wavy wall ( n ). The Prandtl number and Lewis number are kept fixed at Pr = 6.2 and Le = 2 . The effect of these parameters are revealed in terms of streamlines, isotherms, isoconcentrations, entropy generation, average Nusselt number and Sherwood number. Results indicate that heat and mass transfer rate augment as Rayleigh number and volume fraction of nanoparticles increase and are found to drop with the increase in Hartmann number and buoyancy ratio., (© 2019 The Authors.)